1. Field of the Invention
The present invention relates to improved cooling structure for a triphasic alternator rectifier such as commonly used on automotive vehicles. More specifically, it relates to an improved air cooled heat sink device which provides more surface area and better air flow on such an alternator. More generally it relates to a heat sink device which is well adapted to partially encircle any rotary electromotive machine in close proximity to the rotors of that machine. As such it is particularly well adapted to provide cooling for the control circuitry of any modern motor, generator, or alternator, used in a setting where fluid flow is available for cooling. The cooling fluid may be a gas or liquid or both.
Fields most likely to benefit from the advantages of the instant invention include the transportation, manufacturing, and home appliance industries, as well as any industry dependent on electromotive machinery for power generation. Examples include electric lawn mowers, heating ventilation and air conditioning motors, mixing and blending machinery, and auxiliary power generation on all sorts of vehicles. These are but several examples of possible applications.
Thus it can be seen that the potential fields of use for this invention are myriad and the particular preferred embodiment described herein is in no way meant to limit the use of the invention to the particular field chosen for exposition of the details of the invention.
A comprehensive listing of all the possible fields to which this invention may be applied is limited only by the imagination and is therefore not provided herein. Some of the more obvious applications are mentioned herein in the interest of providing a full and complete disclosure of the unique properties of this previously unknown general purpose article of manufacture. It is to be understood from the outset that the scope of this invention is not limited to these fields or to the specific examples of potential uses presented hereinafter.
2. Description of the Prior Art
The use of semiconductor devices in control circuitry for large electromotive machinery is becoming more and more common. The precision of control and generally light weight and small size of the semiconductor devices are advantages which are difficult to ignore. However, there remains a crucial problem with semiconductor devices which has yet to be overcome and that is their sensitivity to heat. Therefore, certain electromotive devices that are required to operate in high temperature areas are prone to premature failure if they use semiconductor control devices.
A common example of this occurs in automotive alternators which are used to generate electrical power for recharging batteries which supply auxiliary electrical power for the vehicle for such devices as lights, windshield wiper motors, radios, etc. The alternator is located in close proximity to the massive heat source of a high powered internal combustion engine. Conventional alternators naturally generate a cyclic alternating current as they are turned by the engine. A steady direct current is required to recharge the conventional wet cell chemical batteries in common use. A rectifier device is needed to convert the alternating current provided by the alternator to the direct current required by the batteries. One such common and inexpensive rectifier can be constructed from six semiconductor diodes and a suitable capacitor connected in a bridge circuit so as to rectify three phase alternating current produced by an alternator. The prior art has disclosed such devices. However problems continue to exist relative to breakdown of the semiconductor diodes due to the excessive heat in the automotive underhood environment. My invention represents a simple and effective means of overcoming these problems with the prior art.
Searches were conducted at the United States Patent and Trademark Office for related inventions and the prior art discovered is discussed herein. As will be seen, the simplicity and effectiveness of my invention is not rivaled in the prior art.
U.S. Pat. No. 4,606,000, issued to Steele et al. on Aug. 12, 1986, shows a bridge rectifier for a diode-rectified alternating current generator. It is comprised of two metallic heat sinks formed respectively of copper and aluminum that are separated by an electrical insulator. Each heat sink carries a plurality of semiconductor diode chips. The diode chips are electrically connected to electrical connectors that are inserted molded to insulator blocks that are supported by one of the heat sinks. The electrical connectors are adapted to be connected to the phase windings of an alternating current generator. The aluminum heat sink has a finned area which is adapted to be contacted by cooling air when the bridge rectifier is mounted in the generator. The structure of this patent forms the basis upon which the improvement of the present invention is predicated. Therefore, U.S. Pat. No. 4,606,000 is hereby incorporated by reference. By contrast, the device of the instant invention has a thicker finned aluminum heat sink portion so as to present approximately twice the surface area to the air flow and thus effectively double the convective heat transfer. In addition, an undercut circumferential groove has been incorporated into the wall forming the major diameter of the finned aluminum heat sink. This groove is deep enough to intersect the air flow path through the finned aluminum heat sink and provide an additional air flow in the radial direction an provide further improved cooling of the sensitive semiconductor diodes. Also, the additional embodiment of my invention showing separate radial cooling fins in place of multiple apertures through the aluminum heat sink is not shown by Steele et al.
U.S. Pat. No. 4,604,538, issued to Merrill et al. on Aug. 5, 1986, shows an air cooled diode-rectified alternating current generator for use on motor vehicles. The generator has an internal fan located within the slip ring end frame and an external fan located adjacent the outer wall of the drive end frame. The internal fan cooperates with a baffle having a central opening and forces cooling air between air inlet openings and air outlet openings formed on the slip ring end frame. The air that traverses this path cools one end of a stator winding and a bridge rectifier. The external fan causes a flow of air between air inlet openings and air outlet openings formed in the drive end frame and this air contacts an opposite end of the stator winding. The cooling arrangement also provides for a flow of cooling air from the air inlet openings in the slip ring end frame to the air outlet openings in the drive end frame. The patent basically discloses the same dual heat sinks described in the Steele et al. patent above and the instant invention presents the same differences.
U.S. Pat. No. 4,286,186, issued to Hagenlocher et al. on Aug. 25, 1981, shows a vehicular alternator end shield construction. The patent is to facilitate manufacture and provide readily accessible insertion openings for rectifier diodes in automotive alternators. The end covers or end shields are made as sheet metal elements with radially extending arms, leaving space for ventilating openings therebetween, extending from the center of rotation of the alternator, and form with bearing retaining means at the center, for example in the form of a punch or drawn bushing extension extending in an axial direction and at right angles to the major plane of the sheet metal element which, preferably, is also formed with stiffening ribs or beads at the lateral edges thereof. Preferably, the alternator is, in cross section, hexagonal and three arms, extending at 120 degrees with respect to each other, the hexagonal outer end portions, are provided to permit universal fitting of the electrical connections with respect to the rotary position of the alternator shell and thus permit matching of the position of electrical connection to various attachment positions of the shell on a internal combustion engine. By contrast the cover or shell of the instant invention is designed to provide passage of the diode connections through in the radial direction.
U.S. Pat. No. 4,680,495, issued to Chiampas et al. on Jul. 14, 1987, shows a spark protected alternator. It has an external cavity on an end plate of the alternator housing with commutating (slip) rings on an alternator shaft extension and mating metal brushes positioned within the external cavity. The external cavity is effectively sealed from ambient atmosphere surrounding the alternator, to provide protection from sparks generated between the brushes and commutating rings wherein a minimum area of the housing end plate is utilized. Integral extensions of the end plate form side walls of the external cavity that partially radially surround the shaft extension and commutating rings. A brush holder in which the brushes are attached has projections which mate with slots in the side walls to radially close the external cavity, and an end cap (including a gasket) closes an open end of the external cavity, while the end plate effectively closes the other end of the external cavity. The brush holder forms part of the walls that close the external cavity, and this minimizes the size of the external cavity required to seal the commutating rings and brushes from the ambient atmosphere. By contrast, the cover or shell of the instant invention is designed to provide passage of the diode connections through in the radial direction and no particular provision has been made for sealing or spark proofing.
U.S. Pat. No. 5,043,614, issued to Yockey on Aug. 27, 1991, shows an alternator rectifier bridge assembly. An alternator rectifier bridge is incorporated into an alternator housing by inserting half of the diodes of the bridge into apertures formed into an alternator housing end plate which then serves as one output for the alternator and also as a massive heat sink to dissipate heat generated in the diodes. The other half of the diodes of the bridge are inserted into apertures formed in a radiator plate which is embedded into a plastic circuit member together with conductor members which interconnect electrodes of the diodes to stator windings of the alternator and also perform other electrical connections required for efficient manufacture and proper operation of the alternator. The radiator plate serves as the other output for the alternator and also as a heat sink. The plastic circuit member is coupled to the alternator housing end plate such that the electrodes of the diodes embedded therein pass through the plastic circuit member to engage corresponding ones of the conductor members resulting in a compact, highly efficient bridge which is readily assembled, preferably in an automated manner, using a limited number of component parts. A crescent shaped plastic end plate is molded so as to embed several of the electrical components of the rectifier bridge and make the appropriate connections when the plate is fastened to an end wall of the alternator which serves as a heat sink. By contrast, the instant invention has a cover plate which attaches to a separate dual metallic heat sink which does not form an integral part of the alternator. Also, the cooling air ports of the instant invention are provided with side ports, provided by a special undercut groove, which allow air flow in both the longitudinal and radial directions.
U.S. Pat. No. 4,162,419, issued to DeAngelis on Jul. 24, 1979, shows an alternator having improved rectifier cooling. The rectifier assembly of an alternator is provided with improved cooling by improved air flow directed over the semiconductor elements of the rectifier assembly. Improved flow of air is provided by an auxiliary fan blade that is attached to a rotating member in the alternator structure. The fan blade is in proximity to the semiconductor rectifier elements of the rectifier assembly. Air ports are provided in the alternator housing to accommodate this longitudinal air flow and to improve the distribution of cooling air. By contrast, the cooling air ports of the instant invention are provided with side ports, provided by a special undercut groove, which allow air flow in both the longitudinal and radial directions.
U.S. Pat. No. 4,419,597, issued to Shiga et al. on Dec. 6, 1983, shows an alternator assembly having a rectifier device in thermal contact with case and cover. The patent shows; an alternator assembly for an automotive vehicle including a rectifier device composed of a plurality of diodes supported on a negative-side cooling fin of semi-circular shape, a plurality of diodes supported on a positive-side cooling fin of semi-circular arc shape, and a terminal board supporting a plurality of terminals connected to the diodes. The rectifier device is assembled and held in a unitary structure by a plurality of metal members, and arranged in a space defined by an end frame and a rear cover of the alternator assembly in such a manner that the metal members are in contact at one end thereof with the rear cover and at the other end thereof with the end frame. By contrast, the cooling air ports of the instant invention are provided with side ports, provided by a special undercut groove, which allow air flow in both the longitudinal and radial directions.
It will be noted that all the prior art devices provide for air cooling by the flow of air in a single direction regardless of the type of air flow ports or fins, etc. provided. This uni-directional air flow makes these devices inefficient as convective heat transfer devices and thus leads to the aforementioned overheating and semiconductor failures discussed above.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.